In general, a printed circuit board is mainly used for simply electrically connecting a certain functional portion to other functional portion of a device excluding a high-frequency zone to which the characteristic impedance gives an influence. Accordingly, the electric resistance of the conductive paths (circuit patterns) of a printed circuit board has been scarcely taken into consideration of this type.
In the printed circuit board of this type, the conductive paths are formed by juxtaposing plural circuit patterns each having the same width in parallel with a definite interval between them. Therefore, in a printed circuit board having a circuit of a complicated form, for example, when the conductive paths are juxtaposed in a U-shape, the electric resistance of each conductive path differs inevitably from each other. For example, when the conductive paths are juxtaposed in parallel in a U-shape, the length of the conductive path at the inner side portion of the U-shaped conductive paths is different from the length of the conductive path at the outer side portion of the U-shaped conductive paths (the length of the conductive path at the outer side is longer than that of the conductive path at the inner side), whereby the electric resistances of the conductive paths become different from each other. That is, the lengths of the conductive paths in the outer side portion of the U-shaped conductive paths are longer than those of the conductive paths in the inner side portion. Hence the electric resistances of the former are higher than those of the latter.
However, with expansion of the use of printed circuit boards, it has been required to make the electric resistance of each conductive path formed on the printed circuit board same. However, there is actually no practical technique for meeting such a requirement and the development of the technique for meeting the requirement has been keenly desired.